1. Technical Field
The present invention relates to an electronic timepiece for receiving a satellite signal from positional information satellites such as GPS satellites to obtain the current date and time.
2. Related Art
In the global positioning system (GPS) as a system for positioning a self-location, there are used GPS satellites each having an orbit circling around the earth. Further, a GPS device for receiving the satellite signals transmitted from the GPS satellites to obtain the time information and the positional information based on navigation messages included in the satellite signals, and then performing a time correction process and a process for positioning the self-location has been put to practical use.
In a capturing process of the satellite signal transmitted from the GPS satellite, it is common to provide a threshold value for a correlation value or a signal intensity, and receive the satellite signal with a signal level equal to or higher than the threshold value to determine whether or not a subsequent synchronization process and a NAV data decode process can be performed. Thus, it is possible to receive a signal with a quality radio waveform hardly affected by noise or the like, and it becomes possible to improve positioning accuracy and date-time correction accuracy.
Then, in the electronic timepiece configured to be able to switch between a time measurement mode for obtaining the time information and a positioning mode for obtaining the positional information to calculate the location of the electronic timepiece, there has been known a device having the threshold value of the signal intensity in the time measurement mode set to be lower than in the positioning mode (see JP-A-2011-38989 (Document 1)).
The device of Document 1 is capable of capturing the satellite signal low in signal intensity in the time measurement mode, and can therefore shorten the time for capturing the satellite signal. Therefore, the time information can quickly be obtained, and thus the power consumption can also be reduced.
The device of Document 1 described above can shorten the time until the capture of the satellite signal in the case of performing the receiving process in the state in which the electronic timepiece is stationary. However, there has been found out a new problem that in the case in which the user wearing the electronic timepiece is moving, the time until the capture of the satellite signal cannot be shortened in some cases.